1. Field of the Invention
This invention relates to a cathodic protection monitor that is electrically connected to a conventional pole-mounted cathodic protection rectifier that is located above an underground oil, natural gas or water pipe (or storage tank) to reverse the effects of chemical and electrically-induced corrosion which are known to cause a potentially hazardous leak. The cathodic protection monitor receives analog current and voltage signals from the DC output terminals of the rectifier to be digitized, stored and transmitted (by antenna) on demand for analysis so that a determination can be made of the effectiveness of the rectifier and whether the rectifier is in need of repair or replacement.
2. Background Art
As will be explained in greater detail below, an underground natural gas, oil or water pipe or the tank in which such fluids flow or are stored and even an underwater bridge abutment is subject to chemical and electrically-induced corrosion, pitting and deterioration. Such deterioration can lead to leakage which can contaminate the soil above the pipe or tank. In some cases, an explosive condition can occur following pipe or tank erosion. As a consequence of the foregoing, a hazardous environmental condition may be created which will necessitate an expensive cleanup and an interruption of the flow of fluid through the effected pipe. Such a leak and flow interruption recently occurred in Alaska where metal pipes carrying oil were damaged by corrosion.
A known means to combat the negative effects of pipe or tank corrosion is impressed current cathodic protection (ICCP). In this case, a series of cathodic protection rectifiers are mounted on poles that are spaced from one another along the pipe run. Each of the cathodic protection rectifiers supplies a DC output current and voltage to the pipe to be protected and to an underground sacrificial anodic bed lying near the pipe. The function of the cathodic protection rectifier is to reverse the electrical potential through the ground and thereby cause the flow of electrons to travel from the anodic bed to the pipe (or tank) so as to arrest the electrolysis that causes rust and corrosion.
However, the chemical composition and moisture content of the soil in which a pipe or tank is buried often changes over time. Such changing soil conditions may require an adjustment to the cathodic protection rectifier. In other cases, the rectifier may not function properly or fail and be in need of repair or replacement. A common technique for manually monitoring each of the series of pole-mounted rectifiers stationed along the pipeline is inefficient, time consuming, and correspondingly costly.
Accordingly, it would be advantageous to have an electronic monitor connected to the cathodic protection rectifier to efficiently, reliably, and inexpensively collect data that is transmitted from the rectifier to verify the operating characteristics thereof so that the pipe or tank owner or maintenance crew can be alerted as to the need to inspect a suspect rectifier. At the same time, it would also be desirable for a cathodic protection monitor to be able to cause its cathodic protection rectifier to be cycled on and off in synchronization with powering other rectifiers that are stationed along the pipeline so that a government-mandated survey of ground voltage can be completed when all of the rectifiers are repeatedly disabled and then enabled throughout the period during which the survey is conducted.